The present invention relates to a method of inspecting particles that is desirable for fine pattern processing of semiconductor devices such as very large scale integrated circuits (VLSI) and the like.
In recent years, the extent of fineness in pattern processing of such semiconductor devices as VLSI, etc. has been consistently increasing. As the degree of the fineness progresses, the existence of particles such as very small dust particles has affected the yield rates of semiconductor devices.
According to the conventional method, the existence of particles has been examined by irradiating a laser light on a wafer surface and by detecting diffuse light beams which are scattered by particles attached to the wafer surface.
FIG. 6 illustrates how a conventional laser particle inspection apparatus works. A substrate to be inspected 30 is placed on a stage 31. An incident laser light beam 33 from a laser light source 32 is scattered by a particle 34 situated on the substrate to be inspected 30 to throw a diffuse light beam 35. This diffuse light beam 35 is inspected by a light detector 36. The stage 31 is driven into motion by a motor 37. The driving system, the laser source 32 and a light detector 36 are controlled by a controller 38 and the data outputted from the inspection apparatus are processed by a computer 39.
The locations of particles are accurately detected by synchronizing signals for the wafer rotation with signals from the light detector 36. However, it is difficult for the foregoing conventional set-up to detect particles of less than 0.1 .mu.m in dimension because the intensity of the diffuse light beams is too weak to detect.